Real-Time Clock battery pin# (235 PMIC_BBAT) ESD and battery polarity protection?

Hi all,
For a new jetson orin nano customer design, I have the following question:
Is the connector pin# (235 PMIC_BBAT) of the Real-Time Clock from the PMIC before:

  1. reverse battery polarity and
  2. ESD protected?
  3. or is there a protection circuit on the Jetson Nano module?
    I would check the PMIC datasheet myself, but I don’t know which PMIC is used. Currently we protect the connection between the battery and pin# (235 PMIC_BBAT) with a 2k2 resistor. What protection circuit do you suggest?

Thank you very much in advance!

With kind regards

Hi, you can refer to the P2768_A04 schematic in DLC for the pin design. The PMIC for BBAT is MP7960GRE-010F-Z.

Hello Trumany,
thank you very much for your answer.
I had already looked at the P3768_A04 reference design.
The question is whether the diode D4 is superfluous, if the PMIC
has integrated an intene protection against battery polarity reversal.
And when are the resistors R222 and R560 activated? Is it enough to install R222 and R560, without D4?

Another question is, whether the D4 diode fulfills the task of the battery polarity protection or should protect against a charging of the battery, but in the data sheet of the Jetson orin nano it says that only batteries and no e.g. super caps may be connected.

I am trying to get the datasheet of the PMIC MP7960GRE-010F-Z, or do you have it? Because it is not so easily available on the internet

Thank you!

The D4 is to block reverse current. Charging is not supported as said in data sheet. We can’t share the datasheet of 3rd-party device.

Okay, I had thought that charging the battery is not supported by the PMIC and therefore D4 is also superfluous.
Why should I install D4 if no charging function is supported by the PMIC?

That’s what I thought, I asked the manufacturer.
But maybe you can check what the manufacturer describes about the battery reverse polarity protection and the
ESD protection describes in the data sheet

I appreciate your help very much.

There are onboard capacitors on module that might cause reverse current. As said, custom design only needs to follow this reference circuit. If you concern ESD on your board, please add ESD protection accordingly then as there is no external ESD component on module for this pin.

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Thank you, that is a good description, I can start something with it.

Ah, okay, that’s interesting, I wasn’t aware that they have an influence on the PMIC_BBAT pin# 235

Today I received the data sheet from Monolithic Power Systems. They confirm all the information from you.
have another nice week and thank you very much.

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